A constraint solver is encapsulated in a service adapted to participate in a negotiation. In operation, the system constructs a graph in its memory for negotiating a set of actions to be performed by selected ones of a plurality of participants. Each node of the graph defines a negotiation context that has associated therewith a constraint store with at least a set of domain constraints stored therein that limit during the negotiation a set of semantic constraints of the service on variables of the constraint solver.